Water cooling towers

ABSTRACT

An evaporative water cooling tower of the counterflow type, of all-plastic construction, in which the tower housing is formed of two symmetrical mating shells each vacuum-formed from a single sheet of high-impact ABS or other resin material, bonded together at flanged mating edges, having internal shelves formed integrally with the housing shells for supporting plastic evaporator and moisture eliminator grids in the housing, and including a water inlet comprising two intersecting PVC pipes, connected to a spray nozzle at the intersection, between the evaporator and eliminator grids.

United States Patent 1191 Waters June 19, 1973 [54] WATER COOLING TOWERS3,481,114 12 1969 Layfield et al 261/DlG. 11 1 ases: @1212 i;;::;..=:ii'ear/3 18 1? [73] Assignee: Application Engineering Corporation, ElkGrove Village, Ill. Primary ExgzminerTim R. Miles Attorney-James B.Kinzer, Thomas E. Dora and [22] Filed. Dec. 30, 1970 Lloyd L Zickert[21] Appl. No.: 102,776

[57] ABSTRACT [52] U.S. Cl. 55/257, 26l/DlG. l l, 26l/DlG. 1 l2, Anevaporative water cooling tower of the counterflow 220/4 C, 220/73 type,of all-plastic construction, in which the tower [51] Int. Cl B01! 3/04housing is formed of two symmetrical mating shells [58] Field of Search261/016. 11, DIG. 111, each vacuum-formed from a single sheet of high-26l/DIG. 112; 55/257; 220/4 E, 4 C, 73 impact ABS or other resinmaterial, bonded together at flanged mating edges, having internalshelves formed [56] I References Cited integrally with the housingshells for supporting plastic UNITEDSTATES PATENTS evaporator andmoisture eliminator grids in the hous- 2,843,29l 7/1958 Stopps 220 73ingaand incluling water inlet comprising two inter 3,132,190 5/l964Engalitcheff, JIM 261/30 sectlng PVC p1pes, connected to a spray nozzleat the 3,263,853 8/1966 Smith 1. 220/4c intersection, between theevaporator and eliminator 3,286,999 11/1966 Takeda 26l/DIG. 11 g3,454,l87 7/1969 Rees 220/73 9 Claims, 14 Drawing; Figures PATENIEU M 9mSIEHIUZ Q Q QM! P Inventor Charles E.Wa|:ers

- B2, Dow and 2M Marne PAINTED- 3.733.556

Invenl'or Charles E. Waters WATER COOLING TOWERS BACKGROUND OF THEINVENTION There are many applications in which limited cooling ofrelatively large volumes of water is necessary on a continuing basis.For example, various industrial processes may require water cooled fromabout 95F. to a temperature of about 85F. in substantial volume. Similarrequirements may be presented in relatively large air conditioningsystems.

In many of these applications, cooling of the water is effected bypartial evaporation in installations commonly referred to as coolingtowers. In a conventional water cooling tower, the water is dischargedonto an evaporator grid, sometimes called a wet deck, that affords alarge surface area. Air is blown through the evaporator grid, incounterflow to the movement of water along the grid surfaces,evaporating a portion of the water and thereby cooling the remainingwater,

which is collected at the base of the tower and utilized for industrialprocessing, air conditioning, or other purposes. A relatively smallcooling tower installation may have a capacity of about 40 tons; a largemulti-tower installation may exceed 280 tons capacity, on the basis of12,000 BTU per hour per ton with an actual heat rejection from the towerof 15,000 BTU per hour per ton required for refrigeration compressorapplications.

Cooling towers constructed of conventional materials present somesubstantial problems. Because the cooling action of the tower dependsupon evaporation, it is usually desirable to install the cooling toweroutside of the building in which the cooled water is utilized, oftennecessitating a roof installation. Under these circumstances, the weightof the cooling tower, if built of sheet metal, plywood, or otherconventional materials, may pose a substantial structural problem withrespect to roof support. The tower must be rigid enough to withstand asubstantial wind load, when installed out-of-doors. In the operation ofthe tower itself, the entire interior of the housing is continuouslysubject to contact with a flow of water that may be anything but pure,with a consequent high possibility and even probability of corrosion ofconventional metal fittings or rotting of any exposed structuralelements that are not completely impervious to water containing theusual minerals and other impurities. In virtually all applications, itis quite impractical to use distilled water or even de-ionized water,since a part of the water is continuously evaporated to the atmosphereand must be periodically replenished. Because of the requirement forprotection against water damage, cooling towers have been ratherrelatively expensive in construction.

SUMMARY OF THE INVENTION It is a principal object of the invention,therefore, to provide a new and improved water cooling towerconstruction that is light in weight, yet sufficiently strong foroutdoor installation, and that is not subject to deterioration fromcontinuous contact with water from an ordinary supply with a substantialmineral and other impurity content.

A particular object of the invention is to provide a new and improvedcooling tower construction in which virtually the entire cooling tower,from housing through fittings, is constructed of plastic materials.

A specific object of the invention is to provide a new and improvednon-corrosive light-weight cooling tower structure that is relativelylow in cost and that can be erected quickly and inexpensively, yet whichrequires a minimum of maintenance in extended operation.

Accordingly, the invention relates to a water cooling tower comprisingtwo four-sided mating housing shells, each formed from a continuoussheet of high-impact plastic materials, such asan ABS resin, andpreferably of substantially identical configuration, sealed togetheralong mating edges to form a fluid-tight cooling tower housing closed atthe bottom and open at the top and having an air inlet opening in thelower part of one vertical wall, in predetermined spaced relation to thebottom of the housing, for connection to a blower for blowing a streamof air into the bottom portion of the housing. Each housing shellincludes a first integrally formed internal shelf supporting a plasticwet deck evaporator grid that extends across the central portion of thehousing; each housing shell further includes a second integrally formedinternal shelf, supporting a plastic moisture eliminator grid thatextends across and covers the top of the housing. At least-one waterinlet conduit extends across the upper part of the housing,

between opposed vertical walls thereof, intermediate the eliminator gridand the evaporator grid. Nozzle means are connected to the water inletconduit, for spraying water outwardly over the evaporator grid anddownwardly through the cooling tower housing. A water outlet is locatedin the bottom portion of the housing, below the lower edge of theaforesaid air inlet opening.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view,partially cut away, of a water cooling tower constructed in accordancewith a preferred embodiment of the present invention;

FIG. 2 is a plan view of the water cooling tower of FIG. 1;

FIG. 3 is a detail view, partly in section, of a moisture eliminatorgrid incorporated in the water cooling tower of FIG. 1; i

FIG. 4 is a section view of a portion of the evaporator grid of the'cooling tower of FIG. 1, taken approximately along line 4-4 therein;

FIG. 5 is a detail sectional view of a part of the base of the watercooling tower of FIG. 1, taken approximately along line 5-5 therein;

FIG. 6 is a detail sectional view of the joint between the two shellsthat form the housing for the cooling tower of FIG. 1;

FIG. 7 is a perspective view of the cooling tower of FIG. 1 with theblower removed to show additional parts of the housing;

FIG. 8 is a perspective view of a housing shell form ing one half of thecooling tower housing; i

FIG. 9 is a detail section view illustrating the mounting of the waterinlet conduits in the cooling tower,

taken approximately along line 9-9 in FIG. 7;

FIG. 10 is a detail sectional view illustrating the mounting of amake-up water port and a float valve in the housing of the coolingtower, taken approximately FIGS. 13 and 14 are detail sectional views ofdifferent configurations that may be employed for the air inlet openingof the cooling tower.

DESCRIPTION OF THE PREFERRED EMBODIMENT The drawings, particularly FIGS.1 and 7, illustrate a water cooling tower 20 constructed in accordancewith a preferred embodiment of the present invention. Cooling tower 20comprises two four-sided mating housing shells 21 and 22 each formedfrom a continuous sheet of high-impact plastic material; a single shellis illustrated separately in FIG. 8 to afford a better view of the rearof the shell. In the preferred construction, each of the housing shells21 and 22 is preferably formed from a single sheet of high-impactacrylonitrile-butadienestyrene (ABS) material having an opaque acrylicfilm laminated to its external surface for protection againstultra-violet radiation. The sheet has an initial thickness of no morethat about 0.5 inch; a starting thickness of 0.3 inch is preferred.

The plastic sheet forming one of the housing shells 21 and 22 isinitially pre-heated throughout its surface area and is suspended acrossthe open end of a mold having a configuration conforming to therequirements for the shell-The interior of the mold is then evacuated,at a rapid rate, vacuum-drawing the plastic sheet into the mold andforming the housing shell to the required dimensions and configurationin a single operation. Formation of a housing shell is thus effected inone step, although some subsequent trimming and cutting of the shell maybe required. Because of the size of the housing shell (a typical coolingtower may be approximately 4 feet wide by 4 feet deep by 8 feet high)extremely large vacuum molding equipment is necessary; the housingshells for cooling tower 20 may be molded in the equipment usedcommercially for the manufacture of boat hulls.

In molding of housing shells 21 and 22, although a high-impact ABS resinis preferred, other strong impact-resistant plastics suitable formolding in large sheets can be employed. The plastic must affordsubstantial resistance to deterioration in the presence of a continuouswash of the housing interior with ordinary tap water and its attendantimpurities. For added strength, suitable fillers may be used in theplastic material from which the sheets used to form the housing shells21 and 22 are'fabricated. Indeed, the housing shells 21 and 22 can beformed from resin-impregnated fiberglass, if desired, although thisconstruction is usually more expensive than warranted for cooling toweruse.

Along one edge of each of the front and rear walls 23 and 24 and thebottom wall 25, of shell 21, as shown in FIG. 8, there is a relativelywide integral right-angle flange 26. There is no need for acorresponding flange on the side wall 27. Similarly, the front and rearwalls 33 and 34 and the bottom wall 35 of shell 22 are each formed witha relatively wide integral flange 36 that extends continuously along thewall edges.

In the assembly of cooling tower 20, the two housing shells 22 and 23are joined together with their respective flanges 26 and 36 abuttingeach other as shown in FIGS. 1, 6 and 7. As can be seen in the detailview of FIG. 6, the two flanges 26 and 36 mate with a substantialsurface area contact between the two flanges. The resulting jointbetween the housing shells 21 and 22 is sealed by means of an epoxyresin or other appropriate solvent-type adhesive that is compatible withthe plastic materials used in the molding of the shells 21 and 22. Inthe preferred construction illustrated in FIG. 6, the epoxy resin bond37 between housing shells 21 and 22 is reinforced by a plurality ofstaples or other mechanical fastening means 38. When thus joinedtogether, and as shown in FIGS. 1 and 7, the two shells 21 and 22 afforda fluid-tight cooling tower housing that is closed along the bottomformed by the shell walls 25 and 35 but is open at the top.

When the housing shells 21 and 22 are formed, each shell is providedwith an exteriorly projecting section of relatively small depth in eachof the front and rear walls, as illustrated by the projections 41 and 42on the front and rear walls 23 and 24, respectively, of shell 21 (FIG.8). When the two shells are joined together, as described above, therear projection 42 is unmodified and the flanged edge of that projectionis sealed directly to a corresponding projection on housing shell 22 toafford a continuous unbroken back wall for the cooling tower housing.The projection serves no particular function on this part of the coolingtower housing, but permits use of two housing shells made from the samemold.

Before the shells are joined, however, the front of the projection 41 inthe front. wall 23 of shell 21 is cut away. The similar portion of themating shell 22 is also cut away, affording a flanged air inlet opening43 in the front wall of the assembled cooling tower housing. The opening43 is located a short distance above the bottom of the cooling towerhousing (about 10 inches in a typical 8-foot tower) and affords aneffective and convenient means for connecting an air blower 44 to thecooling tower (FIG. 1).

Blower 44 may be of conventional construction and preferably comprises acentrifugal blower powered by appropriate means such as an electricmotor 45. The outlet end of blower 44 comprises a duct 46 having anexternal configuration that conforms closely to the internalconfiguration of the flanges 47 and 48 around the air inlet opening 43(FIG. 7). The construction should be such as to afford an effective andconvenient means for sealing the air inlet opening of cooling tower 20to prevent the escape of water from the tower around the rim of the airinlet opening.

One construction that may be adopted for the flange construction betweenthe cooling tower housing and the blower duct 46 is shown in FIG. 13. Asillustrated therein, flange 47 is of re-entrant construction andincludes a transverse wall 49 positioned for abutting engagement with agasket 51 mounted upon the outer rim of blower duct 46. In addition,flange 47 has a lateral wall 52 that is substantially parallel to ductwall 46, and a part of gasket 51 is interposed between the duct wall 46and the flange surface 52. This construction affords scaling in twodirections and gives substantial assurance of a watertight joint.

Another construction that may be employed for the air inlet opening isillustrated in FIG. 14. As shown therein, the housing flange 47A aroundthe air inlet opening may be of simple angular configuration, incross-section. A rigid plastic reinforcement 52 is bonded to the innersurface of flange 47A at some distance from the outer lip of the flange.Again, as in the previous construction, there is both a transverseabutment surface 49A and a lateral sealing surface 52A,

both of which are engaged by a gasket 51 on the blower duct 46. Othergasket configurations can be adopted; the combination of two surfacesfor sealing engagement is much preferred because the air inlet openingotherwise represents a substantial danger of leakage from the coolingtower. The upper edge of blower duct 46 may be provided with a deflectorvane 50 to direct the air entering tower 20 downwardly as it enters thetower. This avoids a direct blast across the tower onto the rear wall,which could produce undue vibration of the rear wall.

Housing shell 21, as molded, includes an outwardly projecting centralportion 55 that begins immediately above the air inlet opening 43 andthat extends around the complete periphery of the housing shell. Asshown in FIGS. 1 and 8, the lower edge 56 of the outwardly projectingcentral portion 55 in housing shell 21 affords an integral internalshelf for supporting a plastic wet deck evaporator grid 57. The centralportion of housing shell 22 is of corresponding configuration, having anoutwardly projecting central portion 58 that forms an internal integralshelf 59 for supporting the wet deck evaporator grid 57.

As shown in FIGS. 1 and 4, the wet deck evaporator grid 57 is formed ofa multiplicity of thin plastic sheets, such as the sheets 61, 62 and 63(FIG. 4). Sheet 61 is molded, by vacuum molding or other suitabletechniques, to afford a multiplicity of individual projections 64 facingoutwardly of one side of the sheet, with similar projections 65 on theopposite side. The projections 65 on sheet 61 mate with and are bondedto a corresponding multiplicity of projections 66 on the next ,adjacentevaporator grid sheet 62. The back surface of sheet 62 has amultiplicity of individual projections 67 that mate with correspondingprojections 68 on the next grid sheet 63. This construction is continuedacross the full width of cooling tower 20 to afford a complete wet deckevaporator grid that fills the entire central portion of the coolingtower housing.

The plastic sheets that form the evaporator grid 57 may be quite thinand are preferably fabricated from a relatively strong and highlywater-resistant plastic material. The number of projections 65-68 on theindividual grid sheets and the spacing of those projections is notparticularly critical; however, the evaporator grid 57 should afford alarge surface area to aid evaporation in operation of the cooling tower.

The upper rim of housing shell 21 is formed with an encompassingoutwardly projecting portion 71 having a lower edge portion 72 and anupper re-entrant flange portion 73, as best shown in FIGS. 1, 2, 7 and8. The outwardly projecting top portion 71 of housing shell 21 ismatched by a similar outwardly projecting top portion 74 on the otherhousing shell 22. The lower edges 72 and 75 of the projections 71 and 74afford a continuous internal shelf that is an integral part of thecooling tower housing and that provides a support for a plastic moistureeliminator grid 76 that extends across and covers the entire top of thecooling tower housing.

One construction that may be used for the eliminator grid 76 isillustrated in FIGS. 2 and 3. As shown therein, the eliminator grid isformed of a multiplicity of segments of thin plastic material shaped toprovide a very large number of sinuous passageways 80 leading from theinterior of the cooling tower to theoutside air. Grid 76 is preferablyformed from a relatively strong resin materialtthe particular resinemployed is not critical. Grid 76, in most installations, is exposed todirect sunlight and, accordingly, is preferably coated with anappropriate material to prevent deterioration of the plastic as theresult of ultraviolet radiation.

In the upper portion of the housing of cooling tower 20 there are twowater inlet conduits that extend across the housing immediately beloweliminator grid 76 and that join in a cross fitting 77. One of theseconduits 78 extends from the front wall of the housing to the rear wall;the other conduit 79 extends across the housing between the side walls27 and 37. The pipe sections forming the water inlet conduits 78 and 79are formed of plastic; three inch polyvinyl chloride pipe is preferred.The same material is preferably utilized for the cross fitting 77. Aunitary ceramic nozzle 81 is mounted upon the cross fitting 77 inposition to spray water outwardly over the entire area of the evaporatorgrid 57.

A preferred mounting for the water inlet conduits is shown in detail inFIG. 9. As illustrated therein, a small flanged opening 82 is formed inthe wall of the tower housing. A molded plastic adaptor 83 is bonded inplace in opening 82, and is sealed to the flange around the opening toafford a water-tight joint. The inlet conduit, such as conduit 78, isfitted into adaptor 83 and is bonded in place in the adaptor. The outerportion of adaptor 83 comprises a threaded opening; the threadedopenings in three of the adaptors are sealed by suitable means such asthe molded PVC plug 84 shown in FIG. 9. One of the four inlet openingsto the water inlet con duits is connected to the return water line ofthe process equipment or air conditioning equipment with which thecooling tower is used by a suitable pipe (not shown).

The nozzle 81 may be of conventional construction. In the preferredform, as illustrated in the drawings, a single ceramic nozzle isutilized, one which provides a wide spray pattern to spray water overthe entire upper surface of the wet deck grid 57. Multiple nozzle treesor other constructions can be employed if preferred.

The cooled water is withdrawn from cooling tower 20 through a wateroutlet opening located at the center of the bottom wall of the coolingtower. As shown in FIG. 12, the water outlet connection may be affordedby an adaptor plug 86 which may be of the same construction as theadaptors employed for the water inlet connections. The complete adaptormay be utilized if desired, or the upper portion, above the bottom walls25 and 35 of the cooling tower, may be cut; off. If the complete adaptorplug is employed, the upwardly extending portion of the adaptor servesas a dirt leg for the water outlet. If desired, the water and the outletopening may be formed in one of the side walls of the cooling towerhousing so long as it is located substantially below the lower edge ofthe air inlet opening 43 (FIG. 7). However, the bottom walls of the twohousing shells 21 and 22 are preferably inclined downwardly and inwardlyat a slight angle, as is apparent from FIG. 7, and the central locationfor the water outlet in the bottom of the inclined pan formed by the twohousing shells is preferred. A separate drain opening (not shown) mayalso be installed in one of the bottom wall sections 25 and 35 forcleaning purposes.

. One of the points of maximum stress in the housing of cooling tower 20is along the intersection formed by the bottom and side walls of eachshell, such as walls 35 and 40. This is particularly true when the toweris supported by a frame having principal support members that extendfrom front to back ot the tower, as described more fully hereinafter. Toreinforce this portion of each shell, an elongated rigid reinforcingmember is bonded into the corner formed by the bottom and side walls.

Thus, as shown in detail in FIGS. and 7, a reinforcing member 88 isbonded into the corner at the juncture of walls 40 and 35 of shell 22.Reinforcing member 88 is preferably an angle member and may be formed ofaluminum or other corrosion-resistant metal. Preferably, however, member88 constitutes an elongated angle member molded or otherwise formed fromresinimpregnated glass fiber; a polyester resin is preferred. The sheetmaterial forming housing walls 40 and 35 is bonded around andencompasses all of the external surfaces of reinforcing member 88,leaving only one surface exposed with that surface located on theinterior of the cooling tower housing. It is highly desirable that thesheet material extending around the reinforcing member 88 not be undulyweakened, so that the corner of the cooling tower housing remainscompletely sealed. The exposed internal surface of reinforcing member 88may subsequently be covered or painted if desired, but this is notusually necessary, particularly if a water-resistant plastic material isused to form the reinforcement. A similar reinforced construction isused along the bottom edge of the side wall for housing shell 21.

The lower portions of housing shells 21 and 22, below wet deck 57, aresubjected to greater stress than the upper portions of the cooling towerhousing, particularly because a substantial quantity of water maycollect in the bottom of the cooling tower. Accordingly, it may bedesirable to reinforce these portions of the housing walls by bondingrigid reinforcement members such as the rib members 89 into moldeddepressions 91 in the walls as shown in FIGS. 1 and 7 and as illustratedin detail in FIG. 11. The reinforcing ribs 89 may be maintained inposition by suitable resin bonds or other adhesive bonds; sonic weldingcan also be employed. Additional reinforcements may be used as required,particularly around air inlet 43.

It is necessary to provide a means for replacing evaporated water in theindustrial processing or air conditioning system in which cooling tower20 is incorporated. An appropriate make-up water inlet comprising anadaptor 94 is mounted in the front wall of the housing, in shell 21, ashort distance above the lower edge of the air inlet opening 43. A watersupply line can be readily connected to adaptor 94 to afford a means formaintaining a substantially constant water supply in the system. Inthose installations in which the base of cooling tower 20 is to providea reservoir for the system, a float valve is installed in the coolingtower. Adaptor 94 may also be used to provide a support and access meansfor the float valve arm. The float valve may be of conventionalconstruction and, accordingly, has not been illustrated in the drawings.An overflow outlet, comprising an adaptor 93 sealed in wall 23 justbelow the lower edge of opening 43, is also provided. Both of the inletwater and overflow adaptors 94 and 93 are sealed into small openings inthe housing wall and both are preferably formed of polyvinyl chloride orother plastic compatible with the material used for the cooling towerhousing.

Cooling tower 20 is supported upon a simple rectangular frame 96 havingfront and back frame members 97, two external side members 98, and twointermediate support members 99 that extend in parallel spaced relationto side members 98. On a frame such as frame 96, cooling tower 20 iscompletely self-supporting and can be mounted on a roof or other outsidelocation. Blower 44 is mounted upon the two inner frame members 99 toassure relatively accurate alignment with the central air intake opening43 in the cooling tower. Preferably, a plurality of clamps are utilizedto hold thereinforced flanges at the bottom of the cooling tower housingon the outside frame members 98 so that there is no necessity fordrilling through the flanges of the cooling tower housing and hence nosubstantial possibility of creating a leak at this point.

In the fabrication of cooling tower 20, the initial step is the moldingof the two symmetrical housing shells 21 and 22. The front portion ofthe molded projection 41 in the front wall 23 of shell 21 is cut awayand the corresponding portion of the mating shell 22 is also cut away toform the two halves of the air inlet opening 43; this operation can beperformed after assembly of the housing shells if desired. The wet deckevaporator grid 57 and the moisture eliminator grid 76 are assembled.Either or both grids may be assembled complete or may be in two halfsections. The PVC pipes forming the water inlet conduits 78 and 79 arealso assembled to the cross fitting 77. All of these elements of thecooling tower are then brought together, with the grids and the inletconduits positioned within the two housing shells.

A bonding adhesive is applied to the flanged surfaces of the two housingshells and the peripheral flanges of the shells are clamped together toseal the two shells into a complete housing. Removable clamps may beutilized, and the adhesive bond alone may be relied upon to 'maintainthe cooling tower housing shells in sealed relation to each other. Onthe other hand, as described above in connection with FIG. 6, mechanicalfasteners such as staples may be utilized to supplement the adhesivebond and to obtain additional mechanical strength in the long peripheraljoint between housing shells 21 and 22.

The operation of cooling tower 20 is substantially conventional. One ofthe inlets to the conduits 78 and 79 is connected to a return water linefrom the industrial processing equipment or air conditioning apparatuswith which the cooling tower is used. The water outlet 86 is connectedto a suitable pump for pumping water from the tower to the equipment inwhich the cooled water is used. The blower 44 is connected to air inletopening 43 and the make-up water inlet 94 is connected to a suitablesupply of make-up water.

The main stream of water enters tower 20 near the top, through one ofthe conduits 78 and 79, and is discharged in a spray from nozzle 81,across the upper surface of the wet deck evaporator grid 57. As thewater cascades down through the wet deck grid, it is con tacted by arelatively high volume of air moving up wardly through the tower, theair being supplied by blower 44. The counterflow of air evaporates apart of the water so that the water collecting in the bottom of thetower is at a substantially lower temperature than the water enteringthe tower. The cooled water is withdrawn through outlet 86 for use bythe equipment with which the tower is employed. Water losses can be madeup in some other part of the system or may be replenished through amake-up water connection to adapter 94, under the control of a floatvalve, as described above.

Some limited maintenance may be necessary in connection with operationof cooling tower 20. Thus, nozzle 81 may become clogged and requirereplacement. It may be necessary to clean out any accumulation ofmaterial, brought in with the water, from the pan afforded by the bottomwalls 25 and 35 of the tower. It may also be necessary to service afloat valve if employed in connection with the tower. For these limitedmaintenance needs, appropriate access doors may be cut into housingshells 21 and 22 and provided with suitable removable covers, as shownin FIGS. 1 and 7.

Cooling tower is quite inexpensive in construction and is much lighterin weight than towers of similar capacity employing conventionalconstructions. For example, a tower of forty ton capacity built inaccordance with the present invention has an operating weight ofapproximately 1,200 pounds, as compared with a cooling tower of similarcapacity but of conventional construction, for which the weight isapproximately 2,000 pounds. Cooling towers constructed in accordancewith the invention can be assembled back-to-back or side-by-side tocomplete cooling tower installations of increased capacity; two of thetowers located immediately adjacent each other can be directly connectedfor inlet water connections with no additional spacing required betweenthe tower units. The all-plastic construction of the cooling towerassures long life, yet affords adequate strength for outdoorinstallations.

I claim:

1. A water cooling tower comprising:

two four-sided mating housing shells, each formed from a continuoussheet of high-impact plastic material, sealed together along matingedges to form a fluid-tight cooling tower housing closed at the bottomand open at the top and having an air inlet opening in the lower part ofone vertical wall, in predetermined spaced relation to the bottom of thehousing, for connection to an air blower for blowing a stream of airinto the bottom portion of said housing;

said housing shells being symmetrical in configuration and having theirmating edges formed as externally projecting flanges with engagingsurfaces disposed in a common vertical plane;

said air inlet opening being centered on the joint between said housingshells and being encompassed by an externally projecting integral flangeaffording a continuous lateral sealing surface for parallel engagementby a gasket on the outlet duct of an air blower;

each of said housing shells including a first integrally formed internalshelf supporting a plastic wet deck evaporator grid that extends acrossthe central portion of said housing;

each of said housing shells further including a second integrally formedinternal shelf, supporting a plastic moisture eliminator grid thatextends across and covers the top of said housing;

at least one water inlet conduit extending across the upper part of saidhousing, between opposed vertical walls thereof, below said eliminatorgrid and above said evaporator grid;

nozzle means connected to said water inlet conduit, for spraying wateroutwardly over said evaporator grid and downwardly through said coolingtower housing;

and a water outlet located in the bottom portion of said housing, belowthe lower edge of said air inlet opening. 2. A water cooling toweraccording to claim 1 in which each housing shell is vacuum-formed from asingle sheet of high-impact ABS resin having an initial thickness of nomore than about 0.5 inches.

3. A water cooling tower according to claim 1 in which the flanges onsaid housing shells are joined by mechanical fastening means and arealso sealed to gether by a solvent-type adhesive compatible with theplastic material of said shells.

4. A water cooling tower according to claim 1, in which said flangefurther affords. a transverse sealing surface for abutting engagementwith said outlet duct gasket. i

5. A water cooling tower comprising: two four-sided mating housingshells, each formed from a continuous sheet of high-impact plasticmaterial, sealed together along mating edges to form a fluid-tightcooling tower housing closed at the bottom and open at the top andhaving an air inlet opening in the lower part of one vertical wall, inpredetermined spaced relation to the bottom of the housing, forconnection to an air blower for blowing a stream of air into the bottomportion of said housing; each housing shell further comprising anelongated rigid reinforcing member bonded into the corner formed by thebottom wall of the shell and the side wall thereof opposite the otherhousing shell, with an unbroken portion of the plastic material of thehousing shell extending completely around all but one internal surfaceof said reinforcing member;

each of said housing shells including a first integrally formed.internal shelf supporting a plastic wet deck evaporator grid thatextends across the central portion of said housing; each of said housingshells further including a second integrally formed internal shelf,supporting a plastic moisture eliminator grid that extends across andcovers the top of said housing;

at least one water inlet conduit extending across the upper part of saidhousing, between opposed vertical walls thereof, below said eliminatorgrid and above said evaporator grid; nozzle means connected to saidwater inlet conduit, for spraying water outwardly over said evaporatorgrid and downwardly through said cooling tower housing;

and a water outlet located in the bottom portion of said housing, belowthe lower edge of said air inlet opening.

6. A water cooling tower according to claim 5, in which said reinforcingmember comprises an elongated angle member molded of resin-impregnatedfiberglass.

7. A water cooling tower comprising:

two four-sided mating housing shells, each formed from a continuoussheet of high-impact plastic material, sealed together along matingedges to form a fluid-tight cooling tower housing closed at the bottomand open at the top and having an air inlet opening in the lower part ofone vertical wall, in predetermined spaced relation to the bottom of thehousing, for connection to an air blower for blowing a stream of airinto the bottom portion of said housing;

each of said housing shells including a first integrally formed internalshelf supporting a plastic wet deck evaporator grid that extends acrossthe central portion of said housing;

each of said housing shells further including a second integrally formedinternal shelf, supporting a plastic moisture eliminator grid thatextends across and covers the top of said housing;

two water inlet conduits extending across the upper part of saidhousing, between opposed vertical walls thereof, below said eliminatorgrid and above said evaporator grid, said water inlet conduits beingdisposed at right angles to each other and intersecting at a crossfitting, said conduits and said fitting all comprising molded plasticmembers;

nozzle means, connected to said cross fitting joining said water inletconduits, for spraying water outwardly over said evaporator grid anddownwardly through said cooling tower housing;

and a water outlet located in the bottom portion of said housing, belowthe lower edge of said air inlet opening.

8. A water cooling tower according to claim 7, in which said conduitsand said fitting are all formed of polyvinyl chloride.

9. A water cooling tower according to claim 7, in which said nozzlemeans comprises a single ceramic spray nozzle having a widehorizontalspray pattern.

2. A water cooling tower according to claim 1 in which each housingshell is vacuum-formed from a single sheet of high-impact ABS resinhaving an initial thickness of no more than about 0.5 inches.
 3. A watercooling tower according to claim 1 in which the flanges on said housingshells are joined by mechanical fastening means and are also sealedtogether by a solvent-type adhesive compatible with the plastic materialof said shells.
 4. A water cooling tower according to claim 1, in whichsaid flange further affords a transverse sealing surface for abuttingengagement with said outlet duct gasket.
 5. A water cooling towercomprising: two four-sided mating housing shells, each formed from acontinuous sheet of high-impact plastic material, sealed together alongmating edges to form a fluid-tight cooling tower housing closed at thebottom and open at the top and having an air inlet opening in the lowerpart of one vertical wall, in predetermined spaced relation to thebottom of the housing, for connection to an air blower for blowing astream of air into the bottom portion of said housing; each housingshell further comprising an elongated rigid reinforcing member bondedinto the corner formed by the bottom wall of the shell and the side wallthereof opposite the other housing shell, with an unbroken portion ofthe plastic material of the housing shell extending completely aroundall but one internal surface of said reinforcing member; each of saidhousing shells including a first integrally formed internal shelfsupporting a plastic wet deck evaporator grid that extends across thecentral portion of said housing; each of said housing shells furtherincluding a second integrally formed internal shelf, supporting aplastic moisture eliminator grid that extends across and covers the topof said housing; at least one water inlet conduit extending across theupper part of said housing, between opposed vertical walls thereof,below said eliminator grid and above said evaporator grid; nozzle meansconnected to said water inlet conduit, for spraying water outwardly oversaid evaporator grid and downwardly through said cooling tower housing;and a water outlet located in the bottom portion of said housing, belowthe lower edge of said air inlet opening.
 6. A water cooling toweraccording to claim 5, in which said reinforcing member comprises anelongated angle member molded of resin-impregnated fiberglass.
 7. Awater cooling tower comprising: two four-sided mating housing shells,each formed from a continuous sheet of high-impact plastic material,sealed together along mating edges to form a fluid-tight cooling towerhousing closed at the bottom and open at the top and having an air inletopening in the lower part of one vertical wall, in predetermined spacedrelation to the bottom of the housing, for connection to an air blowerfor blowing a stream of air into the bottom portion of said housing;each of said housing shells including a first integrally formed internalshelf supporting a plastic wet deck evaporator grid that extends acrossthe central portion of said housing; each of said housing shells furtherincluding a second integrally formed internal shelf, supporting aplastic moisture eliminator grid that extends across and covers the topof said housing; two water inlet conduits extending across the upperpart of said housing, between opposed vertical walls thereof, below saideliminator grid and above said evaporator grid, said water inletconduits being disposed at rigHt angles to each other and intersectingat a cross fitting, said conduits and said fitting all comprising moldedplastic members; nozzle means, connected to said cross fitting joiningsaid water inlet conduits, for spraying water outwardly over saidevaporator grid and downwardly through said cooling tower housing; and awater outlet located in the bottom portion of said housing, below thelower edge of said air inlet opening.
 8. A water cooling tower accordingto claim 7, in which said conduits and said fitting are all formed ofpolyvinyl chloride.
 9. A water cooling tower according to claim 7, inwhich said nozzle means comprises a single ceramic spray nozzle having awide horizontal spray pattern.